Previous winners of the award include Cooking with Poo, a Thai cookbook by Saiyuud Diwong, whose nickname is Poo, and Goblinproofing One's Chicken Coop, which scooped the prize last year.

Horace Bent, The Bookseller's diarist and the custodian of the prize, said: "The public have chosen wisely. Not only have they picked a title that truly captures the spirit of the prize, they have selected a manual that can help one through life's more challenging and delicate moments."

How to Poo on a Date won the award with 30% of the vote. Run by The Bookseller, this year's contest was one of the closest in the competition history. Joint runners-up, with 23% of the vote, were Are Trout South African? by Duncan Brown, and The Origin of Faeces by David Waltner-Toews.

This year's contest was the closest in the competition's historyPrion Press

“We are very happy and honoured that the public thought our book worthy of first place in this much sought-after prize; we'd have been disappointed to be number two”

- Roland Hall, Prion Press editor

Other entries included Working Class Cats: The Bodega Cats of New York City by Chris Balsiger and Erin Canning, Pie-ography: Where Pie Meets Biography by Jo Packham and How to Pray When You're Pissed at God by Ian Punnett.

Roland Hall, Prion Press book editor, said: "We are very happy and honoured that the public thought our book worthy of first place in this much sought-after prize; we'd have been disappointed to be number two.

"How to Poo on a Date is a humorous self-help title and it means a great deal to the authors, and the rest of the team that put the book together, that it should encounter such a splash of success."

Mats and Enzo have made a name for themselves writing defecation guides. Their previous works include How to Poo on Holiday and How to Poo at Work.

"Yet after Mats and Enzo's win this year, with The Origin of Faeces on the shortlist, and Saiyuud Diwong's Cooking with Poo taking the crown in 2011, an all-too clear trend emerges. Diagram devotees have spoken, and spoken in no uncertain terms: poo wins prizes."

While no cash prize is given for the award, the winner normally receives a "fairly passable" bottle of claret.